Remove unused PLM code (#7)

Remove LayoutAwarePage, SuspensionManager, and other suspend-resume handling code. SuspensionManager::SaveAsync and related methods weren't actually called anywhere. I didn't attempt to remove the serialize/deserialize code at the ViewModel layer, although much of that is likely not needed either.

We may decide we want to persist more state through a suspend-terminate-resume cycle (as the app might have done a long time ago). But if we decide we want that, we should not use a persistence mechanism that's closely coupled to frame navigation.

src/Calculator/App.xaml.cpp

@@ -12,7 +12,6 @@
 #include "CalcViewModel\Common\Automation\NarratorNotifier.h"
 #include "CalcViewModel\Common\AppResourceProvider.h"
 #include "CalcViewModel\Common\LocalizationSettings.h"
-#include "Common\SuspensionManager.h"
 #include "Views\MainPage.xaml.h"
 
 using namespace CalculatorApp;
@@ -283,10 +282,8 @@ void App::OnAppLaunch(IActivatedEventArgs^ args, String^ argument)
             }
         }
 
-        // Create a Frame to act as the navigation context and associate it with
-        // a SuspensionManager key
+        // Create a Frame to act as the navigation context
         rootFrame = App::CreateFrame();
-        //SuspensionManager::RegisterFrame(rootFrame, "AppFrame");
 
         // When the navigation stack isn't restored navigate to the first page,
         // configuring the new page by passing required information as a navigation